Photographic-printing frame.



W. MGDADE.

PHOTOGRAPHIC PRINTING FRAME.

(Applidation file {No Model.)

it mg Patented July 4, I899..

d Oct. 14, 1898 lNVENTOf? m0 Jlf A TTOHNE Y S.

UNITED STATES PATENT" OFFICE.

XVILLIAM MCDADE, OF STRAIGHT, PENNSYLVANIA.

PHOTOGR APHlC-PRINTING FRAM SPECIFICATION forming part of Letters Patent No. 628,347, dated July 4, 1899.

Application filed October 14, 1898. Serial No. 693,499, (No d l.) i

To all whom it may concern:

Be it known that 1, WILLIAM MCDADE, of Straight, in the county of Elk and State of Pennsylvania, have invented a new and useful Improvement in Blue-PrintingApparatus, of which the following is a specification.

Myinventionisin the nature of a novel construction of frame or apparatus for making blue prints or other photographic reproductions from a tracing or stencil sheet. Ordinarily in making blue prints, especially those of large size, it is difficult to get the puckers and wrinkles out of the sensitive paper, (or transparent tracing,) and the result is that as the sensitive paper does not at all points lie close to the tracing imperfect reprod uction of lines occurs. My invention makes available the principle of an inflatable air-pad for this purpose; and it consists in the peculiar construction and arrangement of the printingframe and its valves, as will be hereinafter fully described with reference to the drawings, in which-- Figure l is a side view of the apparatus; Fig. 2, a transverse section on line 2 2 of Fig. 1, and Fig. 3 is a sectional detail of the discharge-valve cap.

In the drawings, A A represent two rectangular wooden frames of suitable size, which at one edge are connected together by hinges a to open and close like a book. One of these framesA has a projecting platen A and the other, A, has a glass panelA the platen A being a little smaller than the frame A, which carries the glass panel, so that the frame A will shut down over and around the platen and allow the glass to lie flat against said platen. This platen consists of a rigid back a, and a soft elastic face a formed of soft rubber and made as an air-tight bag or pad. Connecting with the interior of this bag there is attached to the frame A a rubber, tube b, with a compression-bulb B on its end and valves opening inwardly to the bag. There is also in the middle of the frame A and within its marginal projection an outlet-nipple, c, communicating with the air-bag and arranged to discharge the air-pressure as follows: On the nipple c is screwed a thimble 0, having a valve-seat 0 on the outer side of which there closes avalve 0 around whose stem is wound a spring 0 A perforated plug 0 is screwed into the end of thimble c and compresses the spring c holding the valve on the seat. This valve thus becomes an automaticallyyielding safety-valve that allows the air-pressurewithin the bag to escape when it reaches a pressure dangerous to the glass plate. To vary the pressure at which the safety-valve acts, the plug 0 is screwed in or out and locked in place by aset-screw a. For frames having large plates of glass the safety-valve must be set to work at a lower pressure. This valve being within the marginal projection of the frame A allows the latter to lie flat and is housed and protected thereby.

The mode of operating my blue-print apparatus is as follows: The frame A and its platen are laid flat, and the frame A, with glass panel, which is on top, is turned back on its hinges. A sheet of sensitive paper is then laid upon the platen with its sensitive side out. The tracing or stencil sheet is then laid on top of the sensitive paper and the frame, with glass panel, is shut down over the platen and firmly secured by hooks 0 The bulb B is then compressed a number of times until the air-pad on the platen is inflated and made to swellout and press against the paper and tracing until all puckers and wrinkles are flattened out and the paper made to lie flat and close against the tracing. The frame is then turned with its glass side up to the sun, and the exposure of the sensitive paper through the tracing is made in the usual manner.

By this apparatus very sharp and fine lines are secured in the blue print and all imper fections avoided.

Having thus described my invention, what I claim as new, and desire to secure by Letters Patent, is-

1. A photographic=printing apparatus,con sisting of two frames, one of them having a glass plate, and the other an inflatable air-bag with means for filling it, and an automatic discharge-valve for relieving the glass plate of breaking pressure substantially as de= scribed.

2. Aphotographic-printing apparatus,eon sisting of two frames, one of them having a glass plate, and the other an inflatable air-bag closed, one of said frames A having a glass 10 panel, and the other a raised platen with an air-bag a inflating-bulb B, and air-discharge valve communicating with the air-bag and arranged within the marginal projection of the frame A substantially as and for the purpose described.

WILLIAM McDADE.

WVitnesses:

L. V. LITTLE, W W. BARBOUR. 

